1. Field
The present disclosure is generally related to color and gray content detection in image data so that a billing structure for outputting documents is determined.
2. Description of Related Art
Image data comprises a number of pixels having a number of components that contribute to defining the image, such as color and intensity. The image data generally includes various color or gray levels, which contribute to the intensity of each pixel in the image. Each pixel of the image is assigned a number representing the amount of light or gray level for that space at that particular spot; i.e., the shade of gray in the pixel. Binary image data has two possible values for each pixel, ON (represented by the number “1”) or OFF (represented by the number “0”). Images that have a large range of shades are referred to as grayscale images. For example, grayscale images have an 8-bit value per pixel comprising 256 tones or shades of gray for each pixel in the image (gray level of 0 to 255). Grayscale image data may also be referred to as continuous tone or contone image data. The pixels in a color image may be defined in terms of a color space, typically with a number of values or planes, such as three (e.g. RGB, CIELab) or four (e.g., CMYK—C for cyan, M for magenta, Y for yellow, and K for black).
When outputting image data to an output device (e.g., copier, printer, or multi-function device (MFD)), a percentage scale may be used to identify how much ink is employed for a print job. Such information may typically be used for billing a customer for print jobs. For example, some methods employ a billing strategy based on an estimated amount of ink or toner consumption; others bill customers based on a print mode selection (e.g., draft, standard, color, enhanced, etc.) of the output device. In dynamic print job environments, because printing using black ink or toner is less expensive than using colored ink or toner, billing is often based on the amount of color content contained in the job to be printed. In order to bill customers for color printing, color detection is an important feature required in an image path. Color detection is used to analyze documents for presence of color as well as an amount of color in order to bill customers accordingly. Generally, the higher the presence and amount of color in a document, the higher the cost.
Although pixels in the hardware on the binary output at the back end of the image path can be counted, without knowledge of the user specified color versus gray, or device gray line, the gray content of the original image data can not necessarily be determined. For example, when a PDL interpreter and the copy image path generate a balanced gray using composite gray, then backend pixel counters cannot distinguish intended gray from marked color.
Some systems include counting the number of pixels in the image data of the document to be printed. For example, a number of binary pixels associated with the CMYK color planes may be counted to determine a pixel count for each category of color at the time of marking for output in the image path. Generally, with existing color detection and counting methods, a pixel will be labeled as color when the presence of any one of the C, M, and Y signals is detected. U.S. Pat. No. 8,117,134, filed Oct. 16, 2008 by the same Assignee (Xerox Corporation), which is hereby incorporated by reference in its entirety, proposes a way to count color pixels. Other alternate methods for determining color coverage on a marked page include counting pure black pixels marked on the page separately from the CMY pixels and providing separate paths for the counters. For example, RGB input can be detected and K generated. The K is then passed onto the backend where it is converted to gray balanced CMY.
In solid ink and ink jet products, however, neutral areas of an image are often rendered neutral with a combination of cyan, magenta, yellow, black (CMYK) toner/ink when printing or copying. For example, when separate paths for counters are used, CMYK color commands are limited to the RIP generated composite K, and thus the backend counters will count rendered gray or neutral pixels as color. This can create problems in billing based strictly on marking pixel counts since these “gray” counts may be composed of color toners that mimic gray but are counted towards color. For billing purposes, it is not desirable to charge customer for color pixels that were (are) supposed to be gray. The above-referenced '134 patent, for example, has limitations in handling binary image data.
For copy path images, the C, M, and Y values of a pixel in a composite gray area could be quite different. In such images, many of these pixels can be labeled as color (they may be rendered neutral gray), and thus counted as color pixels, which therefore skews the results used to determine the bill for outputting the document. In a multi-tier billing system, for example, pages/documents are placed into different tiers based on the amount of color content therein. Therefore, the customer may be billed for printing the document at a higher rate even though the output document reflects color pixels that are neutralized or gray. Customers do not wish to be billed for composite gray items or neutral pages if the color is not visible to the human eye on the output document.
Furthermore, other systems are configured to generate gray balanced CMY (to depict black pixels, or composite K) and no pure K, and thus the composite K pixels cannot be separated from the color pixels during the determination and accounting of bills for outputting and marking documents. The copy path does the same.
Accordingly, an improved system and method of determining the amount of visible color content in a marked and output document to more accurately bill customers is desirable.